In recent years, interest has increased in the use of four cycle internal combustion engines as power heads for outboard motors and other marine applications. In prior years, two cycle engines were almost universally utilized four outboard motors and some recreational vehicles. In two cycle engines, the lubricating oil is usually mixed with the fuel and lubricates the pistons and bearings as the fuel-oil mixture is inhaled into the engine through the crank case. This oil is eventually burned as part of the fuel mixture.
Four cycle engines normally utilize a lubricating oil distribution system which is separate from the fuel and the fuel does not usually pass through the crank case en route to the cylinders. Oil is usually recirculated many times in the lubrication system of four cycle engines. One of the simplest lubrication systems provides a mechanical means to splash oil onto the moving parts, where it can work into the bearing spaces and fall, by gravity, back into a reservoir to be splashed back onto the moving parts. An improvement upon this system is the addition of a pump which, by means of passages in the engine, delivers oil under pressure directly to bearing surfaces in the engine. Again, oil forced out of said bearing surfaces or flung or drained off of moving parts can fall into a reservoir, below the engine, usually called a sump or oil pan. Systems which use gravity to return engine oil to the reservoir are referred to as "wet sump" systems. In some applications of internal combustion engines, such as motorcycles, acrobatic airplanes and outboard motors, the position in which the engine is used or stored make relying on gravity to return the oil to the reservoir undesirable. In such cases a pump called a scavenge pump removes excess oil from the engine and returns said oil to the reservoir. A second pressure pump is connected to the reservoir removing from it oil to supply the bearings as needed. Engines which utilize an oil reservoir, served by scavenge and pressure pumps, are generally referred to as being of the "dry sump" type.
Although applicable to engines in many types of services, the removable oil tank invention set forth herein is particularly useful to four stroke dry sump outboard motors. While the dry sump engine continually recirculates the oil in the reservoir, it is desirable to change the oil periodically as it becomes contaminated by products of combustion. The location of engines, particularly in marine applications, can make the operation of changing oil a messy proposition. The removable oil tank permits the oil change operation and replacement of its associated oil filter cartridge to take place ashore where the risk of contaminating the environment is lower and the handling of open oil containers can be carried out with better footing. The invention also seeks to make the attachment and removal of the oil tank, form the internal combustion engine application, easy to perform by using quick disconnect fittings. The invention seeks to remedy this problem by providing a removable oil tank and to simplify the mounting of such a tank and its connection to the oil circulation system of the engine.